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Development of highly nonlinear polarization-maintaining fibers with normal dispersion across entire transmission window
摘要： A determined polarization state of light is required in nonlinear optics applications related to ultrashort and single-cycle light pulse generation. Such short timescales require up to one full octave of the spectral width of light. A fiber-based, pulse-preserving and linearly polarized supercontinuum can meet these requirements. We report on the development—from linear simulations of the fiber structure, through fabrication of physical fibers to their versatile characterization—of polarization-maintaining, highly nonlinear photonic crystal fibers, intended for femtosecond pumping at a wavelength of 1560 nm. A full octave of linearly polarized light around this wavelength would enable the covering of amplification bandwidths of the three major fiber amplifiers, from ytterbium-doped systems up to thulium- and holmium-doped fiber amplifiers, with a coherent, linearly polarized seed signal. At the same time, an all-normal chromatic dispersion profile over an entire transmission window, and a small dispersion of nonlinearity in the developed fibers, would facilitate use of commercially available femtosecond fiber lasers as pump sources for the developed fibers.
关键词： normal dispersion,birefringence,fibers,nonlinear optics
更新于2025-09-23 15:22:29
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Highly Dispersion Tailored Property of Novel Class of Multimode Surface Plasmon Resonance Biosensor Assisted by Teflon and Metamaterial Layers
摘要： In this paper, we describe a novel dispersion tailored properties of surface plasmon resonance (SPR) sensor assisted by Te?on and metamaterial layers. The dispersion property and the excitation methods of surface plasmon (SP) waves have been great signi?cance in sensor design. Most of the time, SPR sensor designed for biosensing has been dual mode and its side lobes in dispersion graph can signi?cantly reduce the sensitivity. We propose a design of as many as ?ve-mode SP sensor assisted by Te?on and metamaterial layers. A new sensing theory for exploring highly dispersion tailored properties of multilayer sensor structure is design for ef?cient biorecognition. The proposed design scheme is able to completely remove the side lobes in the dispersion graph by properly controlling the Te?on layer, thin gold ?lm, and metamaterial thickness for the case of multimode SPR sensor. To the best of our knowledge, dispersion tailored properties of multimode SP sensor assisted by Te?on and metamaterial layers together have not been explored and analyzed. The standard matrix method is applied to calculate the various performance parameters of the sensor. Experimental validation has been done with available results for a speci?c case.
关键词： matrix method,re?ectance,metamaterial,Te?on layer,Group velocity dispersion (GVD)
更新于2025-09-23 15:22:29
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Study of Chromatic Dispersion Impacts on Kramers-Kronig and SSBI Iterative Cancellation Receiver
摘要： Field recovery of single sideband (SSB) signals with direct detection has recently been investigated for short-reach communications. One of the cruxes of such direct-detected transmission system is signal-signal beat interference (SSBI) mitigation without sacrificing spectral efficiency. Among various digital signal processing schemes, Kramers-Kronig (KK) algorithm has attracted considerable interest recently due to its effective mitigation of SSBI, and the phase of signals can be recovered using intensity information. As such, chromatic dispersion (CD) can be digitally compensated. Beside KK algorithm, SSBI can also be sufficiently mitigated iteratively. In this paper, we carry out an 80-Gb/s 160-km transmission experiment to investigate chromatic dispersion impacts on both KK and SSBI iterative cancellation (IC) receiver. It is shown that for KK receiver, optimal carrier-to-signal power ratio (CSPR) values increase with transmission distance. This is because that CD induced peak-to-average power ratio (PAPR) increase violates minimum phase condition, and thus the field cannot be reconstructed accurately, leading to degradation of transmission performance. Consequently, OSNR sensitivity for KK receiver is dependent on CD. In contrast, IC receiver has no limitation of minimum phase condition, and thus exhibits high robustness against CD regardless of CSPRs. Besides, experimental results show that after 160-km transmission at the BER threshold of 10-3, the required OSNR for IC receiver is 1.9 dB lower than that of KK receiver.
关键词： direct detection,Kramers-Kronig receiver,virtual single sideband signal,signal-signal beat interference,Chromatic dispersion
更新于2025-09-23 15:22:29
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Interplay of Bit Rate, Linewidth, Bandwidth, and Reach on Optical DMT and PAM with IMDD
摘要： We theoretically compare the performance of optical discrete multi-tone (DMT) and pulse amplitude modulation (PAM) using intensity modulated, direct detection (IMDD). PAM is a lower cost, lower complexity solution than DMT, however it is more vulnerable to chromatic dispersion on the C band. We compare DMT and PAM taking into consideration the interplay of laser linewidth, fiber length, transmission rate, and channel bandwidth. We use a semi-analytical model to examine bit error rates. We study how system parameters shift the performance advantages between DMT and PAM. Our model can also be used to find the best hardware solution and frequency band for a target modulation format and bit error rate.
关键词： PAM,O-band,C-band,chromatic dispersion,DMT,bandwidth,laser linewidth
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Wireless Communications, Signal Processing and Networking (WiSPNET) - Chennai (2018.3.22-2018.3.24)] 2018 International Conference on Wireless Communications, Signal Processing and Networking (WiSPNET) - Performance Analysis for Mixed Line Rates (MLR) WDM/DWDM Networks Under Various Modulation Techniques
摘要： In recent years, a rapid growth of new technologies requires communication systems to support higher bit rate and longer distance. The Optical network is one of the best optimal solutions which can satisfy the demand for high data rate. The performance of current optical networks depends on the traffic demands. To minimize the traffic mixed line rate (MLR) optical network is implemented. In a transparent MLR optical network, data transmission is done over different wavelength at different line rates within the same fiber. MLR optical networks with data rate 10/40/100 Gb/s over different wavelength channels is a new networking paradigm. This paper considers various modulation techniques in order to achieve better bit error rates (BER). It also shows that modulation technique has a great role in improving the data rates and quality of transmission.
关键词： Wavelength division multiplexing/Dense wavelength division Multiplexing (WDM/DWDM),Bit error rate,Chromatic dispersion,Mixed line rates,Physical layer impairments,Amplifier spontaneous emission
更新于2025-09-23 15:22:29
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Elastic constants and phonon dispersion relation analysis of graphene sheet with varied Poisson's ratio
摘要： Through the achievement of elastic parameter equivalence by the structural mechanics method, the beam–truss space frame model for graphene sheet has been simpli?ed; moreover a representative unit cell of the periodic graphene structure has been extracted. On this basis, the Bloch theorem is combined with the ?nite element method to determine the phonon dispersion relation of graphene. For the widely used thickness values of the carbon–carbon (C–C) bond, the aspect ratios (thickness/length) are so large that the shear deformation should be considered such that as a result, the negative Poisson's ratio (NPR) characteristic of the C–C bond is observed. Analytical expressions for the elastic constants of graphene sheet have been obtained with varied C–C bond Poisson's ratios. The reasonable coherence with previous results reveals the e?ectiveness of the structural mechanics method for analysing the mechanical properties of nanostructures. The e?ect of deformation modes on the phonon dispersion relation of graphene sheet is further discussed; it is concluded that the acoustic phonon modes are sensitive to the deformation modes of the C–C bond, whereas these deformation modes negligibly in?uence the optical phonon modes. The numerical results also reveal that the shear deformation and the resulting NPR e?ect play an important role in the mechanical property analysis of graphene sheet. To summarise, the interrelation between NPR materials and nano materials has stimulated a wide ?eld of research; moreover, numerous novel phenomena have been observed.
关键词： Elastic constants,Poisson's ratio,Phonon dispersion relation,Graphene sheet,Structural mechanics method
更新于2025-09-23 15:22:29
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Interactions between M-typed solitons based on nonlinear optimization in dispersion management systems
摘要： Investigations on soliton interactions in dispersion management systems are beneficial to improving the communication capacity. In this paper, the variable-coefficient fifth-order nonlinear Schr?dinger equation, which can be used to describe the soliton interactions in dispersion management systems, is studied analytically. M-typed soliton interactions are presented based on the obtained soliton solutions. Influences of nonlinear effects on M-typed soliton interactions are analyzed. Results indicate that we can effectively control soliton interactions by means of nonlinear optimization of dispersion management systems.
关键词： Soliton interactions,Solitons,Dispersion management systems
更新于2025-09-23 15:22:29
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Absorption Coefficient Dispersion in Flash Thermography of Semitransparent Solids
摘要： Pulse and flash thermography are experimental techniques which are widely used in the field of non-destructive testing for materials characterization and defect detection. We recently showed that it is possible to determine quantitatively the thickness of semitransparent polymeric solids by fitting of results of an analytical model to experimental flash thermography data, for both transmission and reflection configuration. However, depending on the chosen experimental configuration, different effective optical absorption coefficients had to be used in the model to properly fit the respective experimental data, although the material was always the same. Here, we show that this effect can be explained by the wavelength dependency of the absorption coefficient of the sample material if a polychromatic light source, such as a flash lamp, is used. We present an extension of the analytical model to describe the decay of the heating irradiance by two instead of only one effective absorption coefficient, greatly extending its applicability. We show that using this extended model, the experimental results from both measurement configurations and for different sample thicknesses can be fitted by a single set of parameters. Additionally, the deviations between experimental and modeled surface temperatures are reduced compared to a single optimized effective absorption coefficient.
关键词： Dispersion,Flash thermography,NDT,Absorptance,Infrared thermography,Semitransparency
更新于2025-09-23 15:22:29
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Dispersion of Love waves in size-dependent substrate containing finite piezoelectric and viscoelastic layers
摘要： The dispersion properties of Love waves are utilized for the fabrication of sensor devices in the different material environments. This study involves the propagation of Love wave in a double-layered structure consisting of two finite layers of viscoelastic and piezoelectric material lying over the semi-infinite size-dependent micropolar substrate. The bottom substrate of the structure is modeled as, the material with microstructural properties. The real and damping dispersion relations are obtained analytically in closed form expression under both the cases of electrically open and short conditions. The coupling constant and characteristic length that describe the effect of the microstructure of the micropolar substrate, are studied graphically on Love wave propagation. The effects of piezoelectric layer are shown by considering two different materials of a piezoelectric layer, i.e., PZT-5H or BaTiO3, along with the internal friction and heterogeneity parameter associated with a viscoelastic layer. The numerical computation and the graphs are given for aluminium-epoxy (substrate), viscoelastic material and PZT-5H or BaTiO3 (piezoelectric layer). Some of the particular cases are derived from the study by using different relevant conditions.
关键词： Viscoelastic,Piezoelectricity,Dispersion relations,Heterogeneity,Micropolar,Love wave,Characteristic length
更新于2025-09-23 15:22:29
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A Highly Birefringent and Nonlinear AsSe<formula><tex>$_{2}$</tex></formula>-As<formula><tex>$_{2}$</tex></formula>S<formula><tex>$_{5}$</tex></formula> Photonic Crystal Fiber with Two Zero-Dispersion Wavelengths
摘要： A hybrid AsSe2–As2S5 photonic crystal ?ber (PCF) with a solid elliptical core is proposed and studied theoretically by the full-vector ?nite element method. The core and cladding of the PCF are made of AsSe2 and As2S5 glasses, respectively. Simulation results demonstrates that, at the operating wavelength of 1.55 μm, the proposed PCF not only exhibits a very high birefringence of 0.091 but also has large nonlinear coef?cients of 147.8 and 78.2 W ?1m ?1 for the X- and Y-polarized (X and Y-pol) modes, respectively. Moreover, it is able to achieve two zero-dispersion wavelengths for both the X-pol (1.52 and 2.19 μm) and Y-pol (1.43 and 2.12 μm) modes. The proposed hybrid PCF exhibits excellent polarization maintaining and the nonlinearity performance, thus, suitable to be used in supercontinuum spectrum generation and polarization maintaining nonlinear signal processing.
关键词： zero-dispersion wavelength,High birefringence,supercontinuum spectrum generation,photonic crystal ?ber,nonlinearity
更新于2025-09-23 15:22:29